Oled packaging

ABSTRACT

An improved method of fabricating a device such as OLED is disclosed. The method includes applying an adhesive on a cap or substrate. The adhesive is partially cured to initiate the cross-linking process while remaining in the liquid phase. The cap is then mounted onto the substrate and the adhesive is cured to encapsulate the device. By partially curing the adhesive prior to mounting the cap, the curing of the adhesive can be achieved without prolonged exposure to UV radiation or high temperatures which can adversely impact the device.

FIELD OF THE INVENTION

[0001] The present invention relates to fabrication of devices such asorganic light emitting diodes (OLEDs). More particularly, the inventionrelates to a process for encapsulating or packaging OLEDs.

BACKGROUND OF THE INVENTION

[0002]FIG. 1 shows a conventional OLED device 100. The OLED devicecomprises one or more organic functional layers 110 between first andsecond electrodes 105 and 115 formed on a thin substrate 101. Forflexible devices, the substrate material typically comprises plastic orpolymer, such as PET, PEN, PC, or PES. The electrodes can be patternedto form, for example, a plurality of OLED cells to create an OLED device(e.g., pixelated device, segmented display, or larger area illuminationsource). Bond pads 150, which are coupled to the first and secondelectrodes, are provided to enable electrical connections to the OLEDcells. A cap 160 encapsulates the device to protect the OLED cells fromthe environment such as moisture and/or air.

[0003] Typically, the cap is bonded to the substrate with active OLEDcells using polymeric resin based adhesives. After mounting the cap ontothe substrate, the adhesive is cured. Curing is preferably done by UVinstead of heat due to the low thermal stability of the active layers ofthe OLED device. Current UV processes are ineffective with plasticsubstrates since the substrates filter about 40-60% of the UV radiation,resulting in incomplete curing of the adhesives. To ensure that theadhesive is fully cured, the substrate is subjected to prolonged UVexposure. However, prolonged exposure to UV undesirably cause thesubstrates to become brittle and yellow.

[0004] As evidenced from the above discussion, it is desirable toprovide a process which effectively encapsulates the device withoutaffecting the quality and characteristics of the substrate of activecomponents.

SUMMARY OF THE INVENTION

[0005] The invention relates to fabricating device which includesencapsulating the active components of the device with a cap. In oneembodiment, the components comprise OLEDs. An adhesive is applied to thecap in regions which contact the substrate on which the active device isformed. Providing the adhesive on the substrate in regions contactingthe cap is also useful. In accordance with the invention, the adhesiveis partially cured to initiate the cross-linking process while remainingin a liquid phase. In one embodiment, the pre-cure comprises exposingthe adhesive to radiation for less or equal to about 30 seconds. Afterpartially curing the adhesive, the cap is mounted onto the substrate.The adhesive is then fully cured, thereby encapsulating the device. Thepartial curing of the adhesive prior to mounting the cap advantageouslyenables curing to seal the device without the need of strong curingconditions (high temperatures or prolonged UV exposure).

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 shows an OLED device; and

[0007] FIGS. 2-4 show a process for fabricating a device in accordancewith the invention.

PREFERRED EMBODIMENTS OF THE INVENTION

[0008] FIGS. 2-3 show a process for encapsulating an OLED device inaccordance with one embodiment of the invention. Referring to FIG. 2, acap 160 is shown. In one embodiment, the cap comprises a cavity cap.When mounted on the substrate on which the device is formed, a cavity iscreated to accommodate, for example, the OLED cells. Alternatively, thecap can comprise a flat substrate, as shown in FIG. 3. In suchapplications, the substrate on which the cap is mounted can be preparedwith support structures to create the cavity. Such support structuresare described in, for example, PCT Application No: PCT/SG/00143 filed onDec. 17 1999, titled “Encapsulation For Organic LED Device” (AttorneyDocket Number 99P 8271), which are herein incorporated by reference forall purposes. The cap comprises, for example, metal or glass. Othermaterials, such as polymers (e.g., PET, PC, PES, PEN, PE, PMMAS, PS),are also useful.

[0009] An adhesive 280 is applied to portions 265 of the cap whichcontacts the substrate. Various techniques, such as dispensing, screenprinting and contact printing, can be used to apply the adhesive. Theadhesive comprises, for example, polymeric resin based adhesives such asepoxy or acrylic resins. Other types of adhesives, such as phenolic orbismaleimide, are also useful. Applying the adhesive to the substrate inregions which contact the cap is also useful.

[0010] In accordance with the invention, the adhesive is partially curedprior to mounting the cap onto the substrate. In one embodiment, theadhesive partially cured by exposing it to UV radiation. In oneembodiment, the adhesive is directly exposed to UV radiation for about30 seconds. The pre-curing initiates the cross-linking process in theadhesive but does not harden it. In other words, the adhesive remains asa viscous liquid and not a gel after the partial curing process. Otherpartial curing techniques, such as e-beam, laser, or heat can be used.The curing techniques and conditions may depend of the type of adhesiveused.

[0011] Referring to FIG. 4, a substrate 101 is provided. The substratecomprises, for example, plastic or polymeric material. Plastic orpolymeric materials are particularly useful for fabricating flexibledevices. Such materials include, for example, poly(ethyleneterephthalate) (PET), poly(butylene terephthalate) (PBT), poly(enthylenenaphthalate) (PEN), Polycarbonate (PC), polyimides (PI), polysulfones(PSO), poly(p-phenylene ether sulfone) (PES), polyethylene (PE),polypropylene (PP), poly(vinyl chloride) (PVC), polystyrene (PS) andpoly(methyl methyleacrylate) (PMMA). Other materials which can serve asa substrate are also useful.

[0012] In one embodiment, the substrate is processed to include OLEDcells in the active area on a surface thereof. The cap 160 is mounted onthe substrate 101. The device is then subjected to a final curingprocess to complete the curing of the adhesive. In one embodiment, thefinal curing process comprises thermal curing. The thermal curing, inone embodiment, is performed at a temperature in which the activeorganic layers remain stable. In one embodiment, the adhesive is curedat about 65° C. or less for about 60 minutes or less. The curingencapsulates the OLED device, hermetically sealing the activecomponents. Thus, by partially curing the adhesive in accordance withthe invention, the device can be encapsulated without prolonged exposureto high temperatures or UV radiation which can adversely affect thedevice.

[0013] While the invention has been particularly shown and describedwith reference to various embodiments, it will be recognized by thoseskilled in the art that modifications and changes may be made to thepresent invention without departing from the spirit and scope thereof.The scope of the invention should therefore be determined not withreference to the above description but with reference to the appendedclaims along with their full scope of equivalents.

What is claimed is:
 1. A method for fabricating a device comprising:providing a substrate having active components of the device fabricatedthereon; providing a cap used to encapsulate the active components onthe substrate; applying an adhesive in regions of the cap which contactthe substrate or in regions of the substrate which contacts the cap;partially curing the adhesive, wherein the partial curing initiatescross-linking in the adhesive while remaining in liquid phase; mountingthe cap onto the substrate; and curing the adhesive to encapsulate thedevice.
 2. The method as recited in claim 1 wherein the activecomponents comprise OLEDs.
 3. The method as recited in claim 2 whereinthe adhesive comprises epoxy or acrylic resins.
 4. The method as recitedin claim 2 wherein the device comprises a flexible device.
 5. The methodas recited in claim 4 wherein the adhesive comprises epoxy or acrylicresins.
 6. The method as recited in claim 5 wherein the substratecomprises a polymeric material.
 7. The method as recited in claim 6wherein the adhesive comprises epoxy or acrylic resins.
 8. The method asrecited in claim 2 wherein the substrate comprises a polymeric material.9. The method as recited in claim 8 wherein the adhesive comprises epoxyor acrylic resins.
 10. The method as recited in claim 1 wherein thedevice comprises a flexible device.
 11. The method as recited in claim10 wherein the substrate comprises a polymeric material.
 12. The methodas recited in claim 11 wherein the adhesive comprises epoxy or acrylicresins.
 13. The method as recited in claim 12 wherein the substratecomprises a polymeric material.
 14. The method as recited in claim 1wherein the adhesive comprises epoxy or acrylic resins.
 15. The methodas recited in claim 14 wherein the substrate comprises a polymericmaterial.
 16. The method as recited in claim 1 wherein the substratecomprises a polymeric material.
 17. The method as recited in claim 1wherein the partial curing comprises exposing the adhesive to UVradiation.
 18. The method as recited in claim 17 wherein the curingcomprises thermal curing.
 19. The method as recited in claim 18 whereinthe thermal curing is at a temperature of less than or equal to about65° C.
 20. The method as recited in claim 19 wherein the thermal curingis performed for less than or equal to about 60 minutes.
 21. The methodas recited in claim 18 wherein the thermal curing is performed for lessthan or equal to about 60 minutes.
 22. The method as recited in claim 17wherein the partial curing comprises exposing the adhesive to UVradiation for less than about 30 seconds.
 23. The method as recited inclaim 22 wherein the curing comprises thermal curing.
 24. The method asrecited in claim 23 wherein the thermal curing is performed for lessthan or equal to about 60 minutes.
 25. The method as recited in claim 23wherein the thermal curing is at a temperature of less than or equal toabout 65° C.
 26. The method as recited in claim 25 wherein the thermalcuring is performed for less than or equal to about 60 minutes.
 27. Themethod as recited in claim 1 wherein the curing comprises thermalcuring.
 28. The method as recited in claim 27 wherein the thermal curingis performed for less than or equal to 30 about 60 minutes.
 29. Themethod as recited in claim 28 wherein the partial curing comprisesexposing the adhesive to UV radiation.
 30. The method as recited inclaim 29 wherein the partial curing comprises exposing the adhesive toUV radiation for less than about 30 seconds.
 31. The method as recitedin claim 27 wherein the thermal curing is at a temperature of less thanor equal to about 65° C.
 32. The method as recited in claim 31 whereinthe partial curing comprises exposing the adhesive to UV radiation. 33.The method as recited in claim 32 wherein the partial curing comprisesexposing the adhesive to UV radiation for less than about 30 seconds.34. The method as recited in claim 31 wherein the thermal curing isperformed for less than or equal to about 60 minutes.
 35. The method asrecited in claim 34 wherein the partial curing comprises exposing theadhesive to UV radiation.
 36. The method as recited in claim 35 whereinthe partial curing comprises exposing the adhesive to UV radiation forless than about 30 seconds.
 37. The method as recited in claim 27wherein the partial curing comprises exposing the adhesive to UVradiation.
 38. The method as recited in claim 37 wherein the partialcuring comprises exposing the adhesive to UV radiation for less thanabout 30 seconds.